[Dovecot] dovecot and ntp: Fatal: Time just moved backwards

[Harlan Stenn]

NTP comes with a script, ntp-wait, that is specifically designed to be
used during the boot-sequence for the purpose of waiting until the clock
is sync'd before starting time-sensitive applications.

See http://support.ntp.org/bin/view/Support/StartingNTP4 for more
information.

BCP is:

- Start ntpd as early as possible during the boot sequence
- As late as possible during the boot sequence run ntp-wait,
  before starting things like Dovecot and database servers

H